Formation mechanism and red light emission photoluminescence of single-phase crystalline Eu2O2CO3 nanoplates compared with Y2O3:Eu phosphor.

The photoluminescence properties and formation mechanism of a novel stoichiometric phosphor are presented. Nanoplates of pure single-phase crystalline Eu2O2CO3 oxycarbonate (hexagonal type-II) were synthesized by dry autoclaving under autogenic pressure (under 3 MPa) using an efficient, high yield solid state green-chemistry route that can be extended to other rare-earth oxycarbonate and oxide systems, resulting in the full conversion of a simple commercial precursor in single-crystalline nanoplates with strong visible luminescence. Phosphors made of an oxide host and an active luminescent dopant ion are the commercial standard (i.e., Y2O3:Eu). It is generally considered that the activity of luminescent species, such as Eu3+, is quenched and disappears above a certain concentration of them in the lattice (concentration quenching). The truly stoichoimetric oxycarbonate phosphor without active dopant ions exhibits very strong red emission when excited by different excitations, in the UV and visible range, without any concentration quenching effect. The bright red light emission spectra of the of the photo-excited phosphor nanoplates under UV and visible light excitation is compared with that of a standard Y2O3:Eu commercial red phosphor powder, and the thermal conversion mechanism is proposed to obtain the single-phase stable stoichiometric oxycarbonate nanoplates.